这个句子对吗：He became a successful actor who his father never was

不对，应该写成He became a successful actor who /that his father had never been。who引导定语从句，从句中的be应该是从他父亲生活的某个时刻开始一直到he became a successful actor，强调结果，即父亲没有成为一个成功的演员。

这个句子是对的，who可以当whom用，前后都用过去式就行了，没必要用过去完成式。

句子是对的!!! who his father never was
是宾语从句